mirror of https://github.com/grpc/grpc-go.git
89 lines
2.8 KiB
Go
89 lines
2.8 KiB
Go
/*
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*
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* Copyright 2022 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package clusterresolver
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import (
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"fmt"
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"google.golang.org/grpc/internal/xds/clients"
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"google.golang.org/grpc/internal/xds/xdsclient/xdsresource"
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)
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// nameGenerator generates a child name for a list of priorities (each priority
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// is a list of localities).
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//
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// The purpose of this generator is to reuse names between updates. So the
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// struct keeps state between generate() calls, and a later generate() might
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// return names returned by the previous call.
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type nameGenerator struct {
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existingNames map[clients.Locality]string
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prefix uint64
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nextID uint64
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}
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func newNameGenerator(prefix uint64) *nameGenerator {
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return &nameGenerator{prefix: prefix}
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}
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// generate returns a list of names for the given list of priorities.
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//
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// Each priority is a list of localities. The name for the priority is picked as
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// - for each locality in this priority, if it exists in the existing names,
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// this priority will reuse the name
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// - if no reusable name is found for this priority, a new name is generated
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//
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// For example:
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// - update 1: [[L1], [L2], [L3]] --> ["0", "1", "2"]
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// - update 2: [[L1], [L2], [L3]] --> ["0", "1", "2"]
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// - update 3: [[L1, L2], [L3]] --> ["0", "2"] (Two priorities were merged)
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// - update 4: [[L1], [L4]] --> ["0", "3",] (A priority was split, and a new priority was added)
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func (ng *nameGenerator) generate(priorities [][]xdsresource.Locality) []string {
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var ret []string
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usedNames := make(map[string]bool)
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newNames := make(map[clients.Locality]string)
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for _, priority := range priorities {
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var nameFound string
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for _, locality := range priority {
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if name, ok := ng.existingNames[locality.ID]; ok {
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if !usedNames[name] {
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nameFound = name
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// Found a name to use. No need to process the remaining
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// localities.
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break
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}
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}
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}
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if nameFound == "" {
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// No appropriate used name is found. Make a new name.
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nameFound = fmt.Sprintf("priority-%d-%d", ng.prefix, ng.nextID)
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ng.nextID++
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}
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ret = append(ret, nameFound)
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// All localities in this priority share the same name. Add them all to
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// the new map.
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for _, l := range priority {
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newNames[l.ID] = nameFound
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}
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usedNames[nameFound] = true
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}
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ng.existingNames = newNames
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return ret
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}
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